The invention relates to the use of a switching device for a hydraulic high-pressure system for the operation of hydraulic screw-tensioning appliances.
Hydraulic high-pressure systems are employed for various purposes in many sectors of industry. One field of use is the operation of various tools. These tools should be as small and as handy as possible and be capable of applying very high forces. Examples of tools of this type are hydraulic screw-tensioning appliances. On account of the small construction volume which is desired, it is necessary for the pressure selected in a high-pressure system to be correspondingly high in order to achieve the required forces. The pumps used for this purpose deliver pressures of between 700 and 3000 bar. Valves available hitherto on the market for the control of pressures of more than 1000 bar are designed as hand-operated shut-off valves, whereas, for pressures of up to 1000 bar, directional seat valves actuated directly by means of electromagnetics are known.
As the designation indicates, hand-operated shut-off valves cannot be controlled remotely, while, because of the high forces required for opening or closing, the directly actuated solenoid valves have a very large and heavy build, but are still unsuitable for a pressure of more than 1000 bar.